The present invention relates generally to a wireless communication system, and more particularly to a method for allocating channel frequencies among cells of the system clusters in order to improve frequency utilization efficiency.
The total capacity of a wireless communication system is proportional to the total frequency spectrum available to the system. The capacity herein refers to the number of users the system can service, or the amount of information the system can transfer to or from its users during a certain time period. The system capacity can be increased if the frequency spectrum can be reused repeatedly throughout the system. Repeatedly reusing a common frequency band, hereafter referred as a frequency channel, in various cells in a wireless communication system is referred to as frequency reuse.
Conventional frequency reuse is achieved by allocating a number of channels for a number of cells to form a frequency reuse pattern. A plurality of such patterns are repetitively used to provide a larger communications service coverage. Each one of the patterns contains all of the channels available to the system.
Obviously, the number of cells contained in the frequency reuse pattern, which is typically referred to as the frequency reuse factor k, determines the frequency utilization efficiency. A lower frequency reuse factor means that a same frequency band is reused more frequently, and vice versa. However, the reuse factor k cannot be reduced arbitrarily, because, when the reuse factor k is reduced, the spatial separation between two cells where the same frequency channels are reused is reduced, thereby resulting in higher co-channel interferences.
The conventional approach of allocating the channels is to first set the minimum requirement for the signal-to-interference ratio, and then decide the minimum size of the frequency reuse pattern based on the signal-to-interference ratio requirement. One drawback of the conventional approach is that it is not optimized for the most efficient use of available channel resources. As such, it is desirable to have a method of allocating the channels for the cells that balances the aforementioned competing factors. Specifically, it is desirable to have the method reduce the frequency reuse factor, thereby improving the frequency utilization efficiency.